Discrete Cosine Transform (DCT)

In Fourier Transform basis function is exponential function where signal to be transformed is convoluted with exponential function.

Discrete Cosine Transform is another transform where basis function is cosine function. Energy compaction property of DCT is most useful property because of which data compression is possible with DCT. Because of single analysis function, compression ratio can be increased only with setting transformation coefficient to zero with loss of information. But there are infinite number of analysis in WT so optimum selection of wavelet function maximize the compression ratio with optimum information loss.